Some American states and some Canadian provinces have made it mandatory, or are considering making it mandatory at the present time, for all automobiles to have daylight running lights that are always on whenever the car is in operation. Various proposals have been made for accomplishing this, including the provision of separate daytime running lights, completely independent from the normal nighttime headlamps. Another proposal is simply to include a resistance in the circuit feeding the normal headlights, such that the resistance may be inserted during the daytime, and removed at night when brighter headlights are required.
Both of these prior proposals are expensive, the first because it requires the provision of an entirely separate set of lights, the second because it requires the provision of a resistance, and also the energy wasted in heat through the resistance.
It has also been proposed that the normal or standard headlamps of a car, which are normally connected to the battery in parallel for nighttime operation, be capable of connection in series during the daytime, so that each headlamp will "see" only half of the voltage provided. This will considerably reduce the brightness of each headlamp, and will not seriously decrease the life of the filament being utilized for the daytime lights.
Of particular interest in this connection is U.S. Pat. No. 1,130,969, issued Mar. 9, 1915 to A. H. Fleet. Another patent which describes a circuit for a series or parallel connection of headlamps is U.S. Pat. No. 1,112,903, issued Oct. 6, 1914 to H. H. Ham. Still another patent directed to this same concept is U.S. Pat. No. 1,257,618, issued Feb. 26, 1918 to D. F. Leone. Yet another patent pertinent in this regard is U.S. Pat. No. 1,313,583, issued Aug. 19, 1919 to W. Curtis.
Other patents of more general interest are the following:
U.S. Pat. No. 3,040,207, issued June 19, 1962 to Grontkowski. PA0 U.S. Pat. No. 3,244,934, issued Apr. 5, 1966 to G. L. Webb. PA0 U.S. Pat. No. 3,277,442, issued Oct. 4, 1966 to W. R. Kearney. This patent places a light-sensitive resistor in the circuit of the warning lamps, thereby varying the amount of current flowing through the lamps.
The first four patents described above, all of which disclose the optional series-connection of headlamps for daytime running, require the operator to learn a new procedure, namely to remember to turn on the daytime running lamps when the vehicle is being operated during the day. Many drivers have been operating their vehicles for decades, and would find it difficult to remember unfailingly to turn on daytime running lights using a manual switch, assuming one were provided.
A companion patent application has been filed in Canada, on Sept. 10, 1985, Ser. No. 490,332, which provides a method and apparatus by which daytime running lights may automatically be switched on whenever the automobile is in operation, the circuitry being such that two headlamps are connected in parallel across the battery terminals for normal nighttime operation, but are connected in series across the battery terminals during the day whenever the car is running. This provides a "fail-safe" method which does not require the operator to learn a new operational procedure, or always to remember to do something which he does not normally do.
While the invention of the said Canadian Patent application Ser. No. 490,332 provides a very satisfactory solution to the problem, there are situations in which it would be of advantage not to use the headlamps to provide daytime running lights, but rather to use the signal lights at the front end of the vehicle to provide daytime running lights.
Again, however, it is desirable to have a system which operates automatically, not requiring the operator to remember a new operational procedure, or to perform some task which he does not normally perform.